The present invention relates to a zip fastener, more particularly a coil type or metal type zip fastener and especially a substantially waterproof coil type or metal type zip fastener.
There are zip fasteners using a fastener tape which is usually woven or knitted and comprised for example of polyester. Fastener elements are attached to the fastener tape by for example crimping or moulding the fastener elements onto a reinforced edge of the fastener tape. Alternatively, when the fastener elements are comprised of a continuous coil, the fastener elements are most commonly woven or knitted into the tape or alternatively are stitched to the tape surface at the edge of the tape.
There also exists a requirement for zip fasteners which are waterproof, or more specifically, which allow a garment to be or remain waterproof once the zip fastener has been secured in place. For example, the rigorous requirements of outdoor pursuit garments often require the zip fasteners which are strong, hard wearing and impervious to fluids.
However, a problem exists when trying to attach a zip fastener to a fastener tape and still maintain a waterproof garment or article in that the usual attachment mechanism for the zip fastener to the tape, especially coil type fastener elements, traditionally involves stitching the coil fastener elements to the tape. As a result, needle holes are formed in the tape, which consequently impair the waterproof nature of the zip fastener.
Prior art teaching have sought to solve this problem and waterproof zip fasteners have been disclosed.
In WO2009/068848 (YKK), there is described a waterproof zip fastener which comprises a fabric tape having coupling elements disposed on an edge of the fabric tape and an extruded transparent thermoplastic material provided on a surface of the fabric tape. A pattern is printed on the tape surface and covered by the transparent layer. Whilst WO2009/068848 provides a waterproof zip fastener, both sides of the zip fastener are not sealed, and the edges of the tapes are not covered or sealed.
In EP 0108214, there is described a watertight slide fastener stringer which comprises a series of coupling elements mounted on a watertight stringer tape along a longitudinal edge thereof. Each coupling element includes a pair of upper and lower halves or members disposed one on each side of the stringer tape and joined by at least one integral connector extending through the stringer tape. The stringer tape is coated with an elastomer which joins to the connectors during an injection moulding process in order to prevent water leakage between opposing sides of the coupled fastener stringers.
Whilst in EP 0108214 both the front and back of the web core of the fastener tapes are covered with a resilient and water resistant elastomer, the tapes are covered with the water resistant elastomer prior to securing the coupling elements onto the fastener tapes. This procedure is not however practical when using a coil type fastener because the sewing procedure required to attach the coiled coupling elements to the tapes would damage the water resistant elastomer as a result of the needle holes created during sewing.
In U.S. Pat. No. 6,519,826 (Ortlieb), there is described a fluid tight zip fastener with a sealing port wherein the zip fastener is made of plastic in which spirals in the spiral zip fastener are injection moulded with a thermoplastic elastomer which forms a continuously contoured coating bearing directly on the contiguous edges of the zip fastener strips. When the zip fastener is closed, the coatings are under compression and form a contiguous seal with each other and the zip fastener slider to prevent fluid penetration.
Whilst U.S. Pat. No. 6,519,826 discloses a fluid tight zip fastener, the injection moulded coating which is used to create the fluid tight fastener is only located on one side of the slide fastener and does not extend over the entire width of the tapes, thereby providing the possibility for some ingress of fluid, especially if the injection moulded coating is pierced during the process of being attached to another article.
Furthermore, the bulky nature of the applied thermoplastic elastomer layer will not be suitable for many applications where an aesthetically pleasing and durable waterproof fastener is required.